Machines of this type are known as jigs.
The manufacturers of these machines have often attempted to make the fabric travel at a constant linear speed on its way through the bath (see FR-A-1, 525,192).
The applicant considered that this constant linear speed could be harmful, being the cause of the lack of uniformity of dyeing which is sometimes seen on webs of fabric of a particular length. In fact, the radius of the winding roll which is formed at each moment by the roller itself and by the fabric already wound varies greatly during the passage of the fabric, for example often being from 1 to 3; moreover, the centrifugal acceleration .gamma. to which the fabric is subjected at the moment when it winds on, varies in the same ratio, but inversely, that is to say from 3 to 1, when the speed is constant, according to the mathematic relations: Y=.omega..sup.2 R=.omega.v=v.sup.2 /R wherein .gamma. is the centrifugal acceleration, .omega. is the angular speed of the winding roller, R is, at each moment, the radius of the whole consisting of the roller and of the fabric wound on it, and v is the linear (or tangential) speed of the fabric given by the relation v=.omega.R.
The quantity of bath and consequently of dye retained by the fabric therefore varies appreciably, and this can give rise to the defect mentioned above.